Erect
/ɪˈɹɛkt/
adjective
Upright; vertical or reaching broadly upwards.
(of body parts) Rigid, firm; standing out perpendicularly, especially as the result of stimulation.
“The penis should be fully erect before commencing copulation.”
(of a man) Having an erect penis
“OK, baby, I'm erect now. Let's get it on!”